U.S. patent application number 13/773172 was filed with the patent office on 2013-08-22 for light curtain.
This patent application is currently assigned to Leuze electronic GmbH + Co. KG. The applicant listed for this patent is Leuze electronic GmbH + Co. KG. Invention is credited to Armin Mueck, Bernhard MUELLER, Robert Schedlberger, Arnold Schoenleitner.
Application Number | 20130214124 13/773172 |
Document ID | / |
Family ID | 47561489 |
Filed Date | 2013-08-22 |
United States Patent
Application |
20130214124 |
Kind Code |
A1 |
MUELLER; Bernhard ; et
al. |
August 22, 2013 |
LIGHT CURTAIN
Abstract
The invention relates to a light curtain for detecting objects
within a monitored region. The light curtain comprises an
arrangement of transmitters that emit light rays, an arrangement of
receivers for receiving the light rays, and an evaluation unit.
Object detection signals are generated in the evaluation unit in
dependence on the receiving signals present at the outputs of the
receivers. The light curtain is divided into sub-regions containing
a specified number of transmitters and receivers. The individual
sub-regions can be adjusted individually through separate parameter
settings. A separate evaluation is realized in the evaluation unit
for the individual sub-regions.
Inventors: |
MUELLER; Bernhard;
(Herrenberg, DE) ; Mueck; Armin; (Pliezhausen,
DE) ; Schoenleitner; Arnold; (Purkersdorf, AT)
; Schedlberger; Robert; (Bad Zell, AT) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Leuze electronic GmbH + Co. KG; |
|
|
US |
|
|
Assignee: |
Leuze electronic GmbH + Co.
KG
Owen/Teck
DE
|
Family ID: |
47561489 |
Appl. No.: |
13/773172 |
Filed: |
February 21, 2013 |
Current U.S.
Class: |
250/206.1 |
Current CPC
Class: |
G01V 8/20 20130101 |
Class at
Publication: |
250/206.1 |
International
Class: |
G01V 8/20 20060101
G01V008/20 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 21, 2012 |
DE |
102012101368.3 |
Claims
1. A light curtain for detecting objects within a monitored region,
comprising: an arrangement of transmitters for emitting light rays,
an arrangement of receivers for receiving the light rays, and an
evaluation unit configured to generate object detection signals in
dependence on signals present at outputs of the receivers, the
light curtain having a plurality of sub-regions, each sub-region
having a predetermined number of transmitters and receivers,
wherein each sub-region can be adjusted individually through
separate parameter settings, and wherein the evaluation unit is
further configured to separately evaluate each sub-region.
2. The light curtain of claim 1, wherein the evaluation unit is
further configured to generate separate object detection signals
for each sub-region.
3. The light curtain of claim 1, wherein the evaluation unit is
further configured to link separate results from each sub-region to
form complex final results.
4. The light curtain of claim 3, wherein the evaluation unit is
further configured to logically link the separate results from each
sub-region to form complex final results.
5. The light curtain of claim 3, wherein the evaluation unit is
further configured to link the separate results from each
sub-region via arithmetic operations.
6. The light curtain of claim 3, wherein the evaluation unit is
further configured to link time-dependent the separate results from
each sub-region.
7. The light curtain of claim 1, wherein the evaluations for
sub-regions are dependent on results of evaluations of other
regions.
8. The light curtain of claim 1, further comprising: a transmitting
unit having transmitters for emitting light rays, the transmitting
unit provided on a first edge of the monitored region; a receiving
unit having receivers for receiving light rays, the receiving unit
provided on a second edge of the monitored region; wherein the
first edge of the monitored region is arranged opposite the second
edge of the monitored region, wherein one transmitter and an
oppositely arranged receiver form a transmitter/receiver pair.
9. The light curtain of claim 8, wherein each sub-region comprises
a number of successively following transmitter/receiver pairs.
10. The light curtain of claim 1, wherein the number and dimensions
for the sub-regions can be varied.
11. A method for detecting an object within a monitored region with
a light curtain, the light curtain having an arrangement of
transmitters, an arrangement of receivers, and an evaluation unit,
the method comprising: emitting light rays from the arrangement of
transmitters, receiving the light rays with the arrangement of
receivers, generating object detection signals in the evaluation
unit in dependence on signals present at the outputs of the
receivers dividing the light curtain into sub-regions with
respectively a predetermined number of transmitters and receivers,
adjusting the sub-regions individually through separate parameter
settings, and realizing a separate evaluation in the evaluation
unit for each sub-region.
12. The method of claim 11, further comprising generating separate
object detection signals in the evaluation unit for the individual
sub-regions.
13. The method of claim 11, further comprising linking results
obtained for each sub-region in the evaluation unit to form complex
final results.
14. The method of claim 13, further comprising logically linking
results determined for each sub-region in the evaluation unit to
form complex final results.
15. The method of claim 13, including linking the results
determined in the evaluation unit for the individual sub-regions
via arithmetic operations.
16. The method of claim 13, wherein the results determined in the
evaluation unit for the individual sub-regions are linked
time-dependent.
17. The method of claim 10, wherein the evaluations for sub-regions
are dependent on results of evaluations of other sub-regions.
18. The method of claim 10, further comprising providing the light
curtain on a first edge of the monitored region with a transmitting
unit with transmitter for emitting light rays, and providing on a
second edge of the monitored region, which is arranged opposite the
first edge, an arrangement of receivers that receive the light
rays, wherein respectively one transmitter and an opposite arranged
receiver form a transmitter/receiver pair.
19. The method of claim 18, wherein each sub-region comprises a
number of successively following transmitter/receiver pairs.
20. The method of claim 10, wherein the number and dimensions for
the sub-regions can be varied.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application claims the priority of German Patent
Application DE 10 2012 101 368.3, filed on Feb. 21, 2012, the
subject matter of which is incorporated herein by reference.
TECHNICAL FIELD
[0002] Embodiments of the present invention relate to a light
curtain for detecting objects.
BACKGROUND
[0003] Light curtains in general function to detect objects in a
monitored region and may comprise a transmitting unit with an
arrangement of transmitters that emit light rays and a receiving
unit with an arrangement of receivers for receiving the light rays.
The transmitting unit and the receiving unit are arranged on
opposite edges of the monitored region, such that if the monitored
region is clear, the light rays from a transmitter impinge on an
associated receiver, positioned on the opposite side. This
transmitter/receiver pair forms a beam axis for the light curtain.
The individual beam axes of the light curtain are activated
cyclically, one after another. For this, a control unit is
integrated into the transmitting unit which actuates a shift
register in such a way that the individual transmitters are
activated cyclically, one after another. An evaluation unit is
integrated into the receiving unit which actuates a different shift
register, such that the individual receivers are also activated one
after another, wherein the activation of the transmitters and the
receivers is synchronized either optically or electronically. As a
result of this synchronization, the individual transmitter/receiver
pairs of the light curtain are activated cyclically, one after
another.
[0004] In order to generate an object detection signal in the form
of a binary switching signal, an evaluation of the receiving signal
amplitude is realized in the evaluation unit with the aid of one or
several threshold values. A test is conducted within one cycle,
during which all transmitter/receiver pairs are successively
activated, to determine whether the light rays of at least one beam
axis are interrupted. If that is the case, the evaluation unit
emits an object message for the switching signal state. If no beam
axis is interrupted, the switching signal state indicates a clear
monitored region.
[0005] One essential disadvantage of such light curtains is that
the evaluation is restricted purely to detecting the presence of an
object. More complex evaluations, in particular local resolution
evaluations, are possible only to a limited degree.
SUMMARY
[0006] It is an object of embodiments of the present invention to
provide a light curtain of the aforementioned type which has a
higher functionality with low design expenditure.
[0007] The above and other objects are accomplished according to
embodiments of the present invention. Various embodiments and
modifications of the invention are described herein.
[0008] According to an embodiment of the invention, there is
provided a light curtain for detecting objects within a monitored
region. The light curtain comprises an arrangement of transmitters
that emit light rays, an arrangement of receivers for receiving the
light rays, and an evaluation unit. In this evaluation unit, object
detection signals are generated in dependence on the signals
present at the outputs of the receivers. The light curtain is
divided into sub-regions containing respectively a predetermined
number of transmitters and receivers. The individual sub-regions
can be individually adjusted with the aid of separate parameter
settings. A separate evaluation is realized in the evaluation unit
for the individual sub-regions.
[0009] According to another aspect of the present invention, there
is provided a method for detecting an object within a monitored
region with a light curtain, the light curtain having an
arrangement of transmitters, an arrangement of receivers, and an
evaluation unit, wherein the method comprises emitting light rays
from the arrangement of transmitters, receiving the light rays with
the arrangement of receivers, generating object detection signals
in the evaluation unit in dependence on signals present at the
outputs of the receivers, dividing the light curtain into
sub-regions with respectively a predetermined number of
transmitters and receivers, adjusting the sub-regions individually
through separate parameter settings, and realizing a separate
evaluation in the evaluation unit for each sub-region.
[0010] The individual sub-regions of the light curtain form
individual, completely functional logical light curtain units which
respectively make possible separate object detections. In contrast
to several light curtains which are physically separate, the light
curtain according to the present invention has a considerably
simpler and more cost-effective design since only a single
evaluation unit is needed for the individual logical light curtain
units and additional sensor components and casing arrangements can
also be utilized jointly.
[0011] According to an embodiment of the present invention, the
individual sub-regions of the light curtain can be parameterized
separately and thus also differently, so that the individual
sub-regions can be adapted to different application requirements.
The type of signal evaluation can also be embodied differently for
the individual sub-regions and can thus be adapted to different
application conditions.
[0012] The different sub-regions can be used to detect different
object structures, respectively with a high degree of detection
sensitivity, as a result of the individual parameter settings,
especially through specifying different response sensibilities for
the receivers, as well as an evaluation that is adapted
thereto.
[0013] According to an embodiment of the present invention, the
number and size of the sub-regions can be varied.
[0014] The sub-regions may furthermore be adapted to different
application conditions with respect to number and size.
[0015] The adaptation of the sub-regions and the setting of
parameters, as well as the evaluation mode may be specified during
a configuration process before the start of the light curtain
operation. This allows the user a simple and quick adjustment of
the light curtain and its adaptation to different applications.
[0016] According to an embodiment of the present invention,
separate object detection signals are generated in the evaluation
unit for the individual sub-regions.
[0017] The individual sub-regions may form completely independent
light curtain units in which separate object detections take place
and, depending thereon, separate object reports are issued. The
object detection signals can be the same or different for the
individual sub-regions. The object detection signal for one or
several sub-regions can thus be a binary switching signal which
only indicates the presence of an object in the respective region.
The object detection signal can furthermore also supply additional
information such as the size and position of the object. A flexible
multi-region monitoring is thus possible with the light curtain
embodied in this way.
[0018] According to an embodiment of the present invention, the
results obtained in the evaluation unit for individual sub-regions
can be combined into a complex final result.
[0019] A super-imposed logic unit is thus provided, meaning an
additional evaluation plane, in which the individual evaluation
results for the individual sub-regions can be combined into
higher-order information, especially for the detection of complex
actions and structures. This additional function may be made
available without additional structural expenditure since the
evaluation unit, which is used for evaluating the signals from the
individual sub-regions, may also be used for realizing these
higher-order evaluations.
[0020] According to an embodiment of the present invention, results
determined in the evaluation unit for the individual sub-regions
are linked logically to form complex final results.
[0021] For example, individual objects detected in the different
sub-regions can be linked via AND, respectively OR linkages, for
which an exemplary embodiment is the control of objects being
conveyed on a multi-belt conveyor.
[0022] According to that embodiment of the present invention, a
light curtain sub-region may be defined for each belt and one
requirement can be that an object is conveyed parallel on each
belt. To check this, the individual object detections in the
sub-regions can be recorded with an AND link in the evaluation
unit.
[0023] According to an embodiment of the present invention, the
results determined in the evaluation unit for the individual
sub-regions are linked through arithmetic operations.
[0024] The counting of objects may furthermore be realized with
arithmetic operations. If objects are conveyed parallel on a
multi-belt conveyor, for example, a light curtain region can be
defined for each belt, wherein the objects detected in the
individual sub-regions are then counted parallel in the evaluation
unit. Alternatively, the sizes or widths of the objects detected in
the individual sub-regions can also be added up.
[0025] According to an embodiment of the present invention, the
results determined for individual sub-regions are linked
time-dependent in the evaluation unit.
[0026] A time-dependent tracking is possible with this type of
embodiment, for example, wherein it is possible in particular to
check whether objects move along defined paths.
[0027] According to an embodiment of the present invention, the
evaluations of some sub-regions depend on the results of
evaluations of other sub-regions.
[0028] This embodiment permits an automatic adaptation of the light
curtain to specific edge conditions, meaning an automatic
optimizing of the light curtain operation is achieved.
[0029] For example, through a suitable adaptation of the evaluation
in dependence on the measuring results obtained for one or several
sub-regions, the reaction sensitivities of receivers in defined
sub-regions can be adjusted automatically in such a way that
objects to be expected in these sub-regions can be detected with
high detection certainty.
[0030] A further embodiment of the present invention relates to the
automatic adaptation of the light curtain evaluation during the
time-dependent tracking of objects. One example thereof is the
tracking of an object path for which it is necessary that an object
detected in a sub-region must have left this sub-region at the
completion of a specified time period.
[0031] The evaluation realized in the evaluation unit then takes
the form of a timer being started in the respective region as a
reaction to the object detection. The evaluation in the sub-region
is thus changed, such that an alarm is generated once the timer
indicates that the specified time period has been exceeded during
the registration of the object in the sub-region.
[0032] According to an embodiment of the present invention, a light
curtain may comprise a transmitting unit with transmitters that
emit light rays, wherein this unit is mounted at one edge of the
monitored region. The light curtain may furthermore comprise a
receiving unit with receivers for receiving the light rays, wherein
this receiving unit is mounted on a second edge of the monitored
region, opposite the first edge. Respectively one transmitter and
an opposite-arranged receiver form a transmitter/receiver pair.
[0033] The individual transmitter/receiver pairs thus form
individual light barriers for which the light rays define the light
axes used to for scanning a monitored region within which an object
can be detected.
[0034] Each sub-region may comprise a number of successively
arranged transmitter/receiver pairs.
BRIEF DESCRIPTION OF THE DRAWINGS
[0035] These and other features and advantages of the invention
will be further understood from the following detailed description
of embodiments with reference to the accompanying drawings in
which:
[0036] FIG. 1 represents a schematic drawing of an exemplary
embodiment of a light curtain according to the invention;
[0037] FIG. 2 shows an exemplary embodiment of the light curtain
according to FIG. 1.
DETAILED DESCRIPTION
[0038] FIG. 1 shows an exemplary embodiment of the light curtain 1
according to an embodiment of the present invention. The light
curtain 1 comprises a transmitting unit 2 with a first casing 2a
and a receiving unit 3 with a second casing 3a. The transmitting
unit 2 and the receiving unit 3 are positioned at opposite edges of
a monitored region, within which objects are detected with the
light curtain 1.
[0039] Positioned inside the casing 2a for the transmitting unit 2
is a linear arrangement of transmitters 5 for emitting light rays
4. The casing 3a for the receiving unit 3 comprises a linear
arrangement of receivers 6 for receiving light rays 4, wherein the
number of receivers corresponds to the number of transmitters 5.
The transmitters 5 may be light-emitting diodes, laser diodes or
the like. The receivers 6 may be photodiodes. A beam-forming
transmitting optic which is not shown herein may be arranged
downstream of the transmitters 5. A receiving optic for focusing
the light rays 4 onto the receivers 6 may be arranged upstream of
the receivers.
[0040] A receiver 6 is arranged opposite each transmitter 5, as can
be seen in FIG. 1, such that with a clear monitoring region, the
light rays 4 emitted by a transmitter 5 impinge on the associated
receiver 6. The transmitter 5 and the receiver 6 thus form a
transmitter/receiver pair which forms a so-called beam axis for the
light curtain 1, wherein eight such beam axes are provided in the
present embodiment. The number of beam axes for a light curtain 1
can vary. Also possible are arrangements for which the light rays 4
of a transmitter 5 may impinge on several receivers 6.
[0041] A first control unit 7 for controlling and activating the
transmitters 5 may be located in the transmitting unit 2. A second
control unit 8 for controlling and activating the receivers 6 may
be located in the receiving unit 3. For the present embodiment, the
control units 7, 8 are shift register arrangements which are
controlled neutrally by a computer unit 9 in the receiving unit 3.
This computer unit 9 may simultaneously function as an evaluation
unit in which the signals present at the outputs of the receivers 6
are evaluated for the object detection. With the evaluation unit,
the outputs of an output circuit 10 may be triggered to output
evaluation signaled generated from the receiving signals.
[0042] With the computer unit 9 and the control units 7, 8, the
individual transmitter/receiver pairs are activated cyclically and
successively, meaning all transmitter/receiver pairs are activated
once during a measuring cycle.
[0043] With the help of a configuration process prior to starting
the operation of the light curtain 1, the transmitter/receiver
pairs may be divided into different sub-regions, wherein it is
possible to variably specify the size and number of the
sub-regions. In general, the sub-regions can also be embodied so as
to overlap. FIG. 2 shows a division of the transmitter/receiver
pairs into two equally large sub-regions I and II, wherein the
first sub-region I comprises the first four transmitter/receiver
pairs and the second sub-region II comprises the last four
transmitter/receiver pairs.
[0044] During the configuration process, different parameter sets
and, in particular, different evaluation methods may be specified
for the individual sub-regions.
[0045] The object detection in the monitored region may be
generally realized in the evaluation unit with the aid of an
amplitude evaluation, in particular a threshold evaluation of the
signals present at the receiver 6. During the configuration
process, the threshold values can be specified as parameters, with
respect to height and number, so that the detection sensitivities
may be specified separately for the individual sub-regions.
[0046] Additionally, specified parameters may be, for example, the
minimum size for the objects to be detected, as well as
time-dependent variables such as desired time periods during which
objects are to be detected. Furthermore specified can be desired
contours of objects which must be detected in individual
sub-regions.
[0047] Furthermore specified can be the type of signal evaluation
for each sub-region, wherein the output signals that are generated
during the object detection, in particular, can be specified for
the individual sub-regions. Finally, specific linkages of output
signals for the individual regions can also be specified during the
configuration process, so that complex final results can be
generated therewith.
[0048] With the exemplary embodiment according to FIG. 2, the light
curtain 1 may be oriented in a vertical plane. A film 11 that is
positioned in a horizontal plane is moved through the region
monitored by the light curtain 1. The film 11 is composed of two
different transparent partial sections 11a and 11b. Both partial
sections 11a and 11b contain holes which are detected with the
light curtain 1. The light rays 4 which pass through these holes
are weakened less than the light rays 4 that impinge on the film
11. As a result of the threshold evaluation of the signals received
at the receiver 6, the holes can therefore be differentiated from
the film material and can be detected.
[0049] The first partial section 11a of the film 11 is detected
with the transmitter/receiver pairs of the first sub-region I of
the light curtain 1. The second partial section 11b of the film 11
is detected with the transmitter/receiver pairs in the second
sub-region II of the light curtain 1. For the detection of holes
and because the partial sections 11a, 11b have a different light
permeability, different threshold values must be specified for the
evaluation of the signals received at the receivers 6 for both
sub-regions I and II during the configuration process. The
evaluation may furthermore be defined during the configuration
process in such a way that a separate object detection signal is
generated for each sub-region I, II. In the process, an object
detection message is output for each sub-region I, II in the form
of an object detection signal if holes are detected therein.
[0050] A super-imposed or higher order evaluation may furthermore
be defined during the configuration process, so that the object
detection signals for both sub-regions I, II are linked. This
linking can be an AND linkage, for example, if it is required that
always two holes must be detected simultaneously in both
sub-regions I, II. Alternatively, the linking can also be a
counting function for which the holes detected in the two
sub-regions I, II are counted.
[0051] It will be understood that the above description of the
present invention is susceptible to various modifications, changes
and adaptations, and the same are intended to be comprehended
within the meaning and range of equivalents of the appended
claims.
* * * * *